When vehicles are stopped, force exerted by an engine and propagated via a transmission or drivetrain generally can be working against braking forces that are applied. When the drivetrain forces are working against the braking forces, the energy being applied can be converted into heat. Some of this heat is generated at the transmission. Excess heat in the drivetrain can result in part wear. Additionally, while at odds, the competing forces from the drivetrain and brake are not producing useful outcomes. Accordingly, the resources expended in creating the force from the drivetrain, such as the fuel consumed by the engine, is wasted.
In other instances, such as when the vehicle is stopped and facing uphill, the forces exerted by the engine and propogated via the transmission aid in keeping the vehicle stationary. Accordingly, braking forces applied that when added to the force being applied via the drivetrain are satisfactory to keep a vehicle stationary, may not be satisfactory to keep the vehicle stationary if such drivetrain forces were not present.